Positioning mechanism for transducing head unit



NOV. 25, 1969 M R ET AL 3,480,934

POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT FIG. I

Filed Aug. 18, 1966 7 Sheets-Sheet 1 I III l I a m I! mh I INVENTORS MERYL E. MiLLER STANLEY R. HUDDLESTON CARL F. WORK fMKZM N 5, 1969 M. E'. MILLER ET 3,480,934

POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT Filed Aug. 18, 1966 7 Sheets-Sheet 2 &29

@QQQ g A x d go I g m INVENTORS MERYL E. MILLER 05 STANLEY R. HUDDLESTON Q CARL F. WORK u.

B amua POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT Filed Aug. 18, 1966 NOV. 25,1969 E. ET AL 7 Sheets-Sheet 5 FIG. 3

INVENTORS MERYL E. MILLER STANLEY R HUDDLESTON CARL F WORK Hyman! KAAIXW 3 u AW HHHU "AU, m l X. HLU

" THEIR ATTOR FIG. 9

CARD I IDENTIFYING REGISTER '7 Sheets-Sheet 4 TRACK IDENTIFYING REGISTER M. E. MILLER ET COMPUTER non 1 TIMING POSITIONING MECHANISM FOR TRANSDUCING HEADIUNIT HEAD POSITION COMPARATOR MATRIX ACTUATOR m w m m E l S S TDS Rum EAEE TIHR L LM NM 0 E E E .R S R W Y IILEF L m mm MSC R. X 2 DD 4 n AORX ECT b um z. 2 n II Q H 8 9 w 2 R w I r m A T EN M HU m f 4 r T m m 1 D a o c 4 E D READ/WRITE CONTROL LOGIC PH OTOCELL Nov. 25, 1969 Filed Aug. 18, 1966 OLD=NEW HOLD m Eg Nov. 25, 1969 M. E. MILLER AL 3,430,934

POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT Filed Aug. 18, 1966 7 Sheets-Sheet-B INVENTORS MERYL E. MILLER STANLEY R. HUDDLESTON CARL E WORK m4 Z5 BYgulma-ilr I FIG.5

Nov. 25, 1969 M, MILLER ET AL 3,480,934

POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT Filed Aug. 18, 1966 7 Sheets-Sheet 7 INVENTORS MERYL E. MILLER STANLEY R. HUDDLESTON CARL E WORK fmzw United States Patent 3,480,934 POSITIONING MECHANISM FOR TRANSDUCING HEAD UNIT Meryl E. Miller, Gardena, Stanley R. Huddleston, Manhattan Beach, and Carl F. Work, Torrance, Calif., assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Aug. 18, 1966, Ser. No. 573,313 Int. Cl. G11b 5/00; B65h 3/44; G06k 7/00 US. Cl. 340-1741 13 Claims ABSTRACT OF THE DISCLOSURE A random access storage arrangement for performing transducing operations on data recorded in parallel tracks on a magnetically coated strip. The arrangement includes an assembled group of strips from which any one strip can be dropped to a rotary capstan transport means adapted to engage and move the strip past a slidably mounted head unit including a plurality of magnetic transducing heads. Actuator means is provided capable of selectively moving the head unit at fixed increments to dispose the transducing heads thereof over predetermined ones of the parallel tracks of the transported strip. Control means which provides a command for selecting the strip and the track thereon to be operated upon also provides for delaying a transducing operation to be performed on the selected track of the transported strip dependent upon whether the head unit must be shifted by the actuator to enable the proper transducing head of the head unit to cooperate with the selected track.

This invention relates to a head assembly that includes a movable head unit having a plurality of magnetic readwrite heads and, more particularly, to means for positioning a head unit for recording information on and receiving information from a multi-track magnetic data processing tape strip or card. I

Magnetically recording information, onto a magnetic I coated recording media is a well known art that is widely used in the computer industry. In one form of magnetic recording, information is recorded on parallel tracks provided on a long tape that is wound on a reel, with each track containing thousands of different items of information. When a particular item is called for by a computer, the tape is searched until that item is detected. With the computer calling for many, many items that are randomly positioned on the tape, much activity and time is required to merely search for the items on the tape.

An improved system of magnetic recording which was designed to overcome the above disadvantage is disclosed in the commonly assigned US. patent application, Ser. No. 12,032. Rather than recording on a few very long tracks, the recording media is formed into short wide tape strips or cards, on which many short tracks are recorded. In such a system the computer need only issue instructions as to which card and which track on the card contains the desired information and very quickly the card can be selected and positioned for read or record operations thereon with very little searching. This system and similar systems are hereafter referred to as card random access memory systems.

The reading and writing operations of previously dis- 3,480,934 Patented Nov. 25, 1969 closed random access memory systems, such as described in the above US. patent application, Ser. No. 12,032, were performed by a plurality of fixed heads mounted on a stationary head assembly. A head was permanently positioned in line with each track of a multi-track magnetic card, and as the card was moved past the head assembly, the head stationed for reading the desired track on the card was activated. In such an arrangement the number of tracks recorded on a card was determined by the number of heads in the head assembly, and inasmuch as the heads were spaced apart on the head assembly, accordingly the tracks were similarly spaced apart on the card.

Each recording head is expensive, and with one head required for each track that is recorded on a card the head assembly is very costly. Furthermore, whereas economical use of the computer equipment demands more compact storage and more rapid access of the recorded information, the spaces on the card that are unrecorded because of the tracks being spaced apart are undesirable.

For these and other reasons, a preferable system includes a head assembly having transducing heads that are movable transversely across the card and enable each head of the head assembly to record on (and/or read) a plurality of tracks. In the apparatus of the present invention, a number of heads are mounted on a movable unit. The heads are spaced apart from each other on the unit, and the movable unit is shifted within the head assembly to locate the heads to positions within the spacings. The tracks can be recorded substantially adjacent to each other on the card (even though the heads are spaced apart on the movable unit) to essentially eliminate the unrecorded spacings.

Generally, in the apparatus of the present invention the heads are spaced apart a distance equal to some multiple of the width of the writing head so that the heads can be shifted into the various positions represented by each width, for operation on a like number of tracks. In the preferred embodiment, the spacing between the heads is equal to the width of three heads. The movable unit is operated by a control system to shift the heads into the appropriate position of the four positions represented by the initial position of the head and the three widths between the heads. The proper head is then activated, all in accordance with controlled timing of the control system, to thereby perform the desired transducing operation on the desired track of a desired card.

Other advantages of the invention will become. apparent by reference to the following detailed description and drawings wherein:

FIG. 1 is a front view of a card random access memory apparatus having a head assembly with transducing heads that are movable in accordance with this invention;

FIG. 1a is a pictorial view illustrating a typical card selecting and releasing means for the apparatus of FIG. 1;

FIG. 2 is an enlarged view taken on lines 22 of FIG. 1 showing the head assembly and actuator therefor in cross-section; 1

FIG. 3 is a perspective view of the head assembly only shown in FIG. 1 with portions removed;

FIG. 4 is a perspective bottom view of the slidable head unit that carries the transducing heads of the head assembly shown in FIG. 3;

FIG. 5 is a cross-sectional view of the slidable head unit as taken on lines 5-5 of FIG. 4;

FIG. 6 is a sectional view of the capstan and head assembly illustrated in FIG. 1;

FIG. 7 is a view of the card release mechanism as taken on lines 7-7 of FIG. 6;

FIG. 8 is a cross-sectional view of the capstan lllUS- trating its relationship to the head assembly and actuator; and

FIG. 9 is a block diagram illustrating the operation of the apparatus of FIG. 1.

Referring to FIG. 1, in a card random access memory apparatus 10, a number of magnetic strips or cards 12 are suspended from a selecting and releasing means 14. The cards 12 are flat, flexible and relatively long in relation to their width and are made, for example, of a flexible polyester such as Mylar (a trademark product of E. I. du Pont de Nemours and Company) coated with a thin layer of iron oxide. With particular reference to FIG. 1a, the cards 12 are disposed on the selecting and releasing means to depend lengthwise by their tabs 120 (formed at the upper edge) from nine horizontally disposed selector rods 122 and two side gating rods 124. The nine selector rods 122 engage the tabs 120 and the two gating rods 124 engage suitable notches provided at opposite sides of the cards. The cards 12 can be released one at a time by rotating certain ones of the selector rods 122 and afterwards the two gating rods 124. The selector rods and two gating rods are rotated by solenoid means 15.

The solenoid means 15 is energized in accordance with a signal from a control unit (to be further described hereafter) to activate the selecting and releasing means 14. In response thereto the selecting and releasing means 14 discriminately releases a desired card 12' that is guided from the selecting means 14 by a card funnel 16 toward and against a rotating capstan 18. A vacuum pressure within the capstan 18 draws the card 12 against the surface of the capstan and the card is caried around the capstan and past a head assembly 20-. A release means 22, upon command, releases the card from the capstan and the card is carried by its momentum through a raceway 24 up and over the selecting and releasing means 14 where it engages a loading mechanism 26 that places the card back on the selector rods 122.

THE HEAD ASSEMBLY As best shown in FIG. 3, the head assembly 20 which is mounted to the apparatus 10 through brackets 21 includes a plurality of write heads 28 and read heads 30 that are carried by a head unit 32 slidably mounted in a housing including side plates 11, front plate 13, carriage base plate 17, vacuum deck plate 19 and back plate 23 (see FIG. 8). The mounting for the head unit 32 is best shown in FIGS. 3-5. Two parallel cylindrical shafts 35 are mounted on brackets 34 of the housing at each side of the head unit 32. Ear portions 36 of the head unit 32, one of which is extended laterally from one side of the head unit 32 and, for purposes of maintaining stability, two of which are extended laterally from the other side, have sleeve-type ball bushings 37 (see FIG. 5) which are mounted on the cylindrical shafts 35. A suitable ball bushing is manufactured by Thomson Industries Inc. of Manhasset, New York, identified as their XA series. Flexible shields 38 enclose the bushings 37 to prevent foreign particles from interfering with the bushings.

In the preferred embodiment, thirty-six of the write heads 28, each having a width of .022 inch, are positioned near the leading edge of the head unit 32. The write heads 28 are spaced apart a distance equal to three times the head width, i.e., .066 inch. Thirty-six of the read heads 30, each having a width of .010 inch, are placed near the trailing edge of the head unit 32 aligned behind the write heads 28. As shown in FIG. 2, each of the transducing heads 30 is provided with a coil 43, and each head is separated from an adjacent head by a spacer 47. The heads and spacers are embedded in the head unit 32 by a potting compound.

The coils 43 of the heads are connected to wires 29 which extend through openings in the side walls 11 of the had assembly 20 (see FIG. 3) to a control unit, e.g. a computer (see FIG. 9). As will be explained more fully in the Operation section hereafter, a card 12' is carried by the capstan 18 to the head assembly and over the heads 28 and 30. In response to a signal from the control unit, a specific head is activated through its wire 29 for writing on or reading a specific track on the card. To aid in guiding the card from the capstan to the heads, the head assembly includes wing portions 31. Referring more particularly to FIG. 6, openings 27 in the leading wing portion are vented to the atmosphere through a passageway 49 and a channel 25 of the head assembly housing to provide a thin air cushion on the card engaging surface of the wing portion to thereby reduce undesirable frictional wear of thecards. Openings 40 and openings 51 in the trailing wing portion are vented to the atmosphere through channels 41 and 42 respectivel in the housing to provide a similar air cushion. A plastic pad 83 on the card engaging surface of the trailing wing portion is provided to further reduce frictional wear of the card tabs as the card is lifted oif the head assembly 20. A vacuum pressure is directed from a vacuum tube (not shown) into a passage 33 (see FIG. 4) within the head assembly that is vented through portals 39 in the head unit 32 adjacent the transducing heads 28 and 30. Thus, during the time a card 12 is carried by the capstan 18 past the head assembly, the card is drawn away from the capstan and held sufliciently close to the heads to permit the desired transducing operation.

THE ACTUATOR The actuator 44 positions the head unit 32, upon command, in any of its four positions within the head assembly housing. Referring particularly to FIGS. 2 and 8, a connecting rod 46 is aflixed at one end to the slidable head unit 32 with the other end of the rod 46 extended into the actuator housing 48 and pivotally connected through connecting pin 53 with a linkage member 50. The linkage member 50 is crosswise to the rod 46 and the pivotal connection is intermediate of the ends of the linkage member. The ends of the linkage member 50 are pivotally connected by pins 55 to plungers 52 and 54 of solenoids 56 and 58, respectively, which are positioned for movement coextensive with the connecting rod 46. The length of the member 50 that is between the pivotal connection with the rod 46 (i.e. pin 53) and the pivotal connection to plunger 52 is one-half of the length of the member 50 that is between pin 53 and the pivotal connection to plunger 54.

The plungers 52 and 54 each carry a flange 57 that is movable within chambers 59 to define the maximum positions of the plungers. The nodules 57' on the flanges permit a movement for each plunger of .066 inch. When the solenoids are both inactive, a compression spring member 61 acting against a collar 64 of a sleeve member 69 aflixed to the rod 46 urges the head unit into its maximum position where the flanges 57 are seated against the forward wall of chamber 59', i.e. away from the solenoids 56 and 58.

When the solenoids are both activated, the linkage member as a unit is pulled against the tension of spring 61 to seat the flanges against the opposite or back walls of chambers 59. When only one of the solenoids is activated, because the pivotal connection of the connecting rod 46 to the linkage member 50' is closer to the pivotal connection of the member 50 with plunger 52 than to the attachment of the member 50 with plunger 54, the position of the plunger 52 has the greatest eifect on the position of the connecting rod and accordingly on the position of the head unit 32. Thus, with solenoid 56 inactive and solenoid 58 active, the flange 57 of plunger 52 will be seated against the forward wall of its chamber 59 and flange 57 of plunger 54 will be seated against the rearward wall of its chamber 59. The distance between the interconnection of the connecting rod 46 to the linkage member 50 and of the linkage member to the plunger 52 is exactly one-third of the distance between the two plungers and thus the connecting rod is moved only one-third the distance moved by plunger 54, i.e., .022 inch. When solenoid 56 is active and solenoid 58 inactive, the movement of the connecting rod 46 is exactly two-thirds the distance moved by the plunger 52, i.e., .044 inch. Thus, the head unit 32 assumes four positions, i.e. when the solenoids are both active and the head unit 32 is in its maximum position toward the actuator, when the head unit 32 is moved .022 inch by deactivating solenoid 58 only (the exact width of a single head), when it is moved .044 inch by activating solenoid 58 and deactivating solenoid 56 (exactly twice the width of a single head), and when it is moved ahead .066 inch by deactivating both solenoids (the total spacing between the heads and exactly three times the width of a single head).

It is desirable to position the head unit very quickly, e.g. in a period of about 25-35 milliseconds, to avoid undue delays in the performance of a subsequent read/ write operation. The rapid intermittent movement of the actuator mechanism induces an undesirable vibration that must be terminated before the transducing operation can be carried out. Thus, in the present appartus the actuator is provided with means for dampening the movement to thereby minimize the vibration.

Such means includes cushion springs 67 positioned between the linkage member 50, at each of the pivotal pin connections 55, and the forward wall of chamber 59. When the respective solenoids are activated, the springs engage the linkage member at a point just prior to the end of the stroke so as to decelerate the movement and reduce the shock that is incurred when the solenoid plunger is stopped. As a further means of dampening, the chamber areas 60 which house the actuator components are filled (through a filler plug 65) with a suitable fluid, e.g. G. E. Silicon Fluid SF96(5) available from the General Electric Company.

The fluid is also contained in chamber 59 which is communicated with chamber 60 through bleed ports 66. Movement of the flanges 57 within the chamber 59 is impeded by the fluid. The extent to which the fluid impedes the movement of the flanges 57 is dependent in part on the ability of the fluid to flow around the flanges and through the bleed ports. Seals 62 are provided to avoid leakage of the fluid around the sleeve member 69 of the rod 46. An expandable bellows membrane 63 in the wall of housing 48 is cornunicated with the fluid in chamber 60 through ports 85 to permit expansion of the fluid when heated by repetitive movement of the actuator components.

THE CAPSTAN The capstan 18 shown in FIGS. 1, 2, 6 and 8 has a cylindrical wall 70 enclosed at one end by end wall 71. As most clearly shown in FIGS. 6 and 8, a driven shaft 72 extends through the capstan and is connected to the end wall 71 for imparting rotative movement to the capstan. A stationary sleeve member 73 is mounted through ball bearings 74 to the shaft 72. Vanes 75 are carried by the stationary sleeve and separate the interior of the rotatable cylinder into stationary chambers 76, 77 and 78. A vacuum source 79 is interconnected with a manifold 80 at the end of the capstan opposite end wall 71 and includes passageways for connecting the vacuum source to the chambers 77 and 78. Vent holes 68 throughout the cylindrical wall 70 produce a suction from the exterior of the capstan into the chambers 77 and 78. Chamber 76 is not connected to the vacuum source and the corresponding exterior of the capstan is not subjected to suction.

The release means 22 shown in FIGS. 6 and 7, comprises a cup member 92 cupped adjacent to the cylindrical wall 70, thereby forming a sub-chamber 93 within the chamber 78. As shown in FIG. 7, portals 91 in the side of the cup member 92 interconnect the sub-chamber 93 with the vacuum of chamber 78. A slidable gate 94 has portals 95 that are aligned with the cup portals 91 in one position to permit the communication, and in a second position the gate portals 95 are offset from the cup portals 91 to prevent such communication. A solenoid means 96 upon command, positions the gate between the two positions. The baffle members 97 connected to the cup member 92 and extended outwardly therefrom within the chamber 78 are provided to concentrate the effect of the vacuum at the point where the card is brought back against the capstan and, when the gate 94 is opened, to also concentrate the vacuum in the sub-chamber 93.

OPERATION Referring generally to the schematic view of FIG. 1, in the operation of the apparatus a card 12' suspended from the selector rods 122 is released by the selecting and releasing means 14 and dropped into the card funnel 16 which guides the card toward and against the rotating capstan 18. The suction from chamber 77 (see FIG. 6) draws the leading edge of the card to the rotating cylinder which grips the card and carries it over the head assembly 20. At the point where the card passes over the exterior of chamber 76, which corresponds to the leading edge of the head assembly, the card is released from the cylindrical wall and (in cooperation with the centrifugal force of the card) is vacuum drawn through the vent holes of head unit 32 toward the head assembly. The momentum imparted to the card by the rotating capstan carries it past the head assembly and chamber 76 where suction from chamber 78 draws the card back into engagement with the capstan.

As the card 12' moves over the head assembly, a specific track is operated on, i.e. information is either read from or recorded on the track. The card is carried around by the capstan and if a second track of the card is to be operated on, the proper head is positioned and activated. When the computer has completed the desired transducing operations on the card, a signal to solenoid means 96 closes the gate 94 of the release means 22 which closes off the suction to the capstan exterior adjacent cup member 92. By centrifugal force and momentum the card is released into the raceway 24 and carried around to the loading mechanism 26.

A system for controlling the various operations is shown in the block diagram of FIG. 9. A computer 100 issues a command comprised of a nine bit binary number to a card identifying register 102 through the nine lines 102a-102i which are coordinated by the timing line 103. The register conveys the command to the solenoid means 15 (FIG. 1) of the selecting and releasing means 14 through lines 14a-14i. The cards supported by the selecting and releasing means 14 are identified by a binary number (e.g. 384 cards, each identified by a separate binary number of the available 512 binary numbers) and the solenoid means 15 of the selecting and releasing means 14 responds to the command to release the card corresponding to the number of the command.

When the command is issued to the card identifying register 102, the computer issues a command which includes an eight bit binary number to a track identifying register 106 through the eight lines 106a106h which are coordinated by timing line 107. This binary number identifies a particular track of the selected card (e.g. one track of 144 tracks on the card, each track identified by one of the 256 available binary numbers). The track identifying register simultaneously conveys the command to a head decoder matrix 108 through the eight lines 108a- 108k and to an actuator decoder matrix 110 through the eight lines 110a110h.

The head decoder matrix 108 identifies from the eight bit binary number, which pair of the 36 pairs of read/ write heads is to be activated for operating on the selected track. The information is converted, eig. for use by a 9 X 4 matrix, and the proper signal is conveyed to the head unit 32 through the thirteen lines 29a29m for setting up that pair of heads for performing the desired transducing operation.

The thirteen lines by coordinate selection select any one of the 36 heads as follows: The 36 heads are divided into four groups of nine heads each. Each of four lines of the thirteen lines are connected to a group and each of nine lines are connected to one of the heads in each group. Any head can thus be activated by energizing the one of four lines controlling the group and the one of nine lines controlling that head within the group.

The actuator decoder matrix 110 identifies from the eight bit binary number, which position of the four positions that the movable head unit is to take to position the selected head for operation on the selected track. The information is converted and the proper signal conveyed to the solenoids 56 and 58 of the actuator 44 through lines 44a and 44b (see FIG. 2).

It takes about 35 milliseconds for the actuator to position the head unit 32 and from about 100 to 200 milliseconds for the card to reach the capstan. Thus, the head unit is in position with respect to the desired set of tracks when the leading edge of the card reaches the capstan. The capstan carries the card past a photocell 109 (or, e.g., a solar cell) to thereby interupt the light beams from the light sources 111 (FIG. 6) which informs the computer through a line 112 and AND gate 116 that the card is in position and ready to be operated on. The light sources 111 are positioned within the capstan and the light beams are directed on the photocell through the vent holes 68 in the cylindrical wall 70 (FIGS. 2 and 8). As the capstan rotates, the light is intermittently interrupted by the cylindrical wall and thus, two light sources are positioned so that at any instant only one of the light sources will be interrupted by the cylindrical wall 70.

In response to the photocell signal, the computer sends a command to a read-write control logic 113. The desired read or write operation is then dictated by the control logic to the pair of read/ write heads selected by the head decoder matrix. A method of checking the head position can be provided by placing a label in the form of a binary code at the beginning of each track of the card. In such a checking process only the read head is operated as the card is first passed over the head assembly, and the label is read in that first pass to establish that the desired track is positioned for operation by the selected heads. When the card again interrupts the light beam of the photocell, the computer through the control logic performs the desired operation.

During the period while the read or write heads are activated, the timing lines 103 and 107 are closed and the computer is prohibited from issuing any commands to the card identifying register 102 and the track identifying register 106. Thus, a situation cannot occur where the actuator 44 would be commanded to set up the head unit 32 for a subsequent operation prior to the termination of the previous transducing operation.

After the first transducing operation is completed, the timing lines 103 and 107 are opened to permit the registers to receive the next command. If there are no further transducing operations to be performed on that card, the next command is to set up the release of the card. When the leading edge of the card subsequently interrupts the photocell the solenoid means 96 is activated to close off suction in the sub-chamber 93 and the card is thrown by centrifugal force onto the raceway 24 and returned to the card loading mechanism 26.

If a second track of the card is to be operated on, the above-mentioned next command will comprise the sending of a new binary code number to the track identifying register 106 through lines 106a-106I1. The head decoder 108 will set up the proper pair of heads to be activated on command from the control logic 113, and the actuator decoder 110 Will establish the proper position for the head unit 32.

Thirty-six of the one-hundred and forty-four tracks on a card are positioned for being operated on by the thirty-six pairs of heads of the head unit. Thus, as many as thirty-six ditferent binary code numbers can be issued by the computer to the track identifying register without having to reposition the head unit. In any of such thirtysix instances the desired pair of heads is electronically selected. In such instances, even though the command from the computer is issued when the leading edge of the card interrupts the photocell, the electronic selection of the desired head is accomplished before the card is engaged by the head unit. Therefore, the transducing operation can be carried out without delay. It is thus preferable to program the computer so that for any one card all of the tracks requiring the same head unit posi tion are selected in sequence so that regardless of the number of tracks to be operated on, the head unit will be repositioned no more than three times (in addition to the initial setting).

When a command from the computer calls for operation on a track that is not aligned with a pair of read/ write heads, the new position of the actuator 44 will be decoded by the actuator decoder matrix 110 and the proper repositioning command Will be conveyed to the actuator. It takes about 35 milliseconds for the actuator to perform the operation of repositioning the head unit. It takes about 45 milliseconds for the capstan 18 to make a single revolution. Thus, if the new command from the computer is sent to the track identifying register 106 when the leading edge of the card has just passed the photocell 109 (so that it will take at least 35 milliseconds before it Will again interrupt the photocell), then the actuator 44 can reposition the head unit 32 in time for the transducing operation to be accomplished when it is subsequently brought into an operative position on the head unit.

If the computer command is issued to the track identifying register 106 when the leading edge of the card has made a partial revolution around the capstan 18, e'g more than about a quarter turn around the capstan from the photocell, then the actuator will still be performing its function of repositioning the head when the card subsequently interrupts the photocell. The read/Write heads can introduce errors into the system by operating on the cards while they are being moved transversely across the tracks. Thus, the system is provided with a delay system that includes a head position comparator 114.

- The new position of the head unit indicated by the decoded command of the actuator decoder 110 is directed through lines 114a and 11412 to the comparator 114. The comparator 114 retains the indicated position of the head unit 32 from the previous command and compares it. with the new position. If the positions are equal then the head unit does not have to be moved and the comparator sends a positive signal to the AND gate 116 through line 1140. The AND gate 116 then, upon receiving the go-ahead signal from the photocell 109, conveys that signal to the computer 100. If the head positions compared by the comparator are not equal, the comparator 114 sends a negative signal to the AND gate 116 and the photocell 109 cannot signal the computer 100 to perform the transducing operation. This negative signal is maintained by a holdover circuit 115 for a period of 35 milliseconds, the time it takes the actuator 44 to reposition the head unit 32. Thereafter, the positive signal is again sent to the AND gate 116 and the photocell 109 (when interrupted by the card) can then convey the goahead signal to the computer 100.

The sequence of operations is repeated until all of the desired tracks of that card have been operated on, whereupon the card will be returned to the card loading mechanism 26 in the manner described. The computer will then signal for the release of the next card.

It is to be understood that this invention is not limited to the specific embodiment described herein but encompasses the full scope defined by the appended claims.

What is claimed is:

1. Apparatus in a random access system for positioning a movable transducing means for cooperating with different tracks of an elongated flexible storage strip selected from a group of strips, said apparatus comprising: a storage means for storing said strips in an assembled group from which any one of said strips can be selectively dropped; a rotary capstan transport means for engaging and transporting a dropped strip through a transducing zone; movable transducing means disposed in said transducing zone in cooperative relationship with said capstan transport means and past which the transport means transports an engaged strip; and control means for specifying a strip and a track on the strip and for controlling the strip selecting operation of said storage means and the position of said movable transducing means such that a transducing operation is performed on a predetermined track of a dropped strip as the strip is transported through the transducing zone by the capstan transport means.

2. Apparatus in accordance with claim 1 including means responsive to the leading edge of a dropped strip transported through the transducing zone by the capstan transport means for initiating the transducing operation performed on said predetermined track of a selected strip.

3. Apparatus in accordance with claim 2 including comparing means responsive to said control means for comparing a newly specified track on a strip being transported by said rotary capstan transport means with a previously specified track on the strip; and means operative when the position of the movable transducing means must be changed to cooperate with the newly specified track to inhibit the initiating means from initiating a transducing operation on the newly specified track the first time the rotary capstan means transports the strip past the transducing zone.

4. In a tape strip access memory system, an assembly having a plurality of magnetic transducing heads that can be moved between different positions for operation on different tracks of a flexible magnetizable storage strip, said assembly comprising a housing having a strip-receiving surface and a head unit slidably mounted in a central :portion of the strip-receiving surface, a plurality of magnetic transducing heads arranged in a row and positioned on the unit coextensive with the sliding movement thereof, the successive transducing heads within the row being spaced apart a distance at least equal to the width of a head and, an actuator interconnected through a connecting rod to the unit, said actuator having means for moving the unit to selectively position the heads within the spacing at fixed increments at least equal to the head width.

5. In a tape strip access memory system, an assembly as defined in claim 4, including a vacuum means interconnected with the housing and being vented to a central portion of the strip-receiving surface for drawing a magnetic strip toward the surface of the transducing heads to perform a transducing operation thereon.

6. 'In a tape strip access memory system, an assembly as defined in claim 5, wherein the spacing between the heads is equal to three times the head width, the actuator components include a linkage member interconnected at a point intermediate of its ends to the connecting rod, a solenoid means connected to each end of the linkage member with the length of the linkage member from the interconnection of the connecting rod to one of the solenoid means being half that of the length between the interconnection and the other solenoid means, and means for selectively energizing the solenoid means to position the head unit in any of four positions.

7. In a tape strip access memory system, an assembly as defined in claim 6, including dampening means contained within the actuator to dampen the shock to the actuator components induced by rapidly moving the head unit to the different operating positions.

8. In a card random access memory system, an assembly as defined in claim 7, including an actuator housing having a plurality of chambers enclosing the actuator components, said dampening means comprising a liquid contained within the enclosure whereby movement of the components is resisted by the presence of the liquid, said chambers being interconnected by portals for the displaced liquid to fiow through, and an expandable membrane provided in the wall of one of the chambers to permit heat-induced expansion of the liquid.

9. A card random access memory system that includes: sending a command in the form of a binary number to a card selecting and releasing means, releasing a magnetic coated card identified by the binary number from the card selecting and releasing means in response to the command, moving the card from the means into transducing operative position with respect to a movable head unit comprised of a plurality of magnetic transducing heads, sending the command in the form of a second binary number that identifies a particular track of the card to the movable head unit and to an actuator for the head unit, decoding the command directed to the head unit to establish the transducing head of the head unit to be activated for performing a desired transducing operation on the track identified by the binary number, decoding the command directed to the actuator to establish the position of the head unit for the selected transducing head to operate on the track identified by the binary number, sensing the released card when it is in operative position with respect to the head unit, and in response thereto performing a desired transducing operation on the selected track of the selected card.

10. A card random access memory system as defined in claim 9, which includes, before the transducing operation, comparing the position of the head unit indicated by the decoded command to the actuator with the position indicated by the previous decoded command, and responsive to the indication of a position change delaying the transducing operation to provide time to complete the position change.

11. In a card random access memory system, a central control; a selecting and releasing means supporting a number of magnetic coated cards; a card identifying register for receiving a command from the central control in the form of a binary code number and for conveying that command to the card selecting and releasing means to selectively release a magnetic card identified by the binary number; a movable head unit having a plurality of magnetic transducing heads; a head decoder; 21 track identifying register for receiving a command from the central control in the form of a binary code that identifies a particular track of the selected card and for conveying that command to said head decoder, said head decoder identifying from the binary number the appropriate transducing head within the head unit to operate on the selected track; an actuator for controlling the position of the movable head unit; an actuator decoder for receiving the command from the track identifying register and for identifying from the binary number the appropriate position of the head unit for the selected head to operate on the selected track; a capstan for receiving the card and directing it past the head unit; and guide means to guide the released card from the card selecting and releasing means to the capstan.

12. In a card random access memory system as defined in claim 11, sensing means positioned with respect to the head unit to sense when the leading edge of the card is in position to be operated on; and a read/write control logic responsive to the sensing means for activating the selected head.

1 1 1 2 13. In a card random access memory system as defined 3,134,097 5/1964 Stevens et a1 340714.1 in claim 12, a head position comparator for receiving the 3,175,204 3/1965 MacDonald 23561.11 decoded command from the actuator decoder and for 3,302,829 2/ 1967 Wilmer 340174.1 comparing the position of the head indicated thereby with 3,349,385 10/ 1967 Studiey 340174.1

the position indicated by the previous command; and 5 means to intercept the signal from the sensing means to STANLEY URYNOWICZ, Primary Examiner the control logic when the two positions are not equal CANNEY Assistant Examiner whereby the transducing operation is delayed to permit time for the actuator to reposition the head unit. L

References Cited 10 235 271 9 UNITED STATES PATENTS 3,105,593 10/1963 Fredkin 340174.1 

